The present invention relates to steps for processing a master optical disk. In particular, it relates to a master-optical-disk processing method, a mastering apparatus provided with the function thereof, a master optical disk processed thereby, and optical disks produced based on the master disk.
In order that the use of a single processing scan may perform laser processing for a groove and prepits in a physical format in which in a land-and-groove-recording rewritable optical medium, the groove and a land are switched for each track, and the prepits (e.g., prepits shifted outward and inward by a half-track pitch from the groove center), which have no track-sector information on spirals identical to those of the groove, are used to enable the reading of the track-sector information on the land and the groove by performing a single processing scan, at least three laser beams are required. In other words, they are: (1) a laser beam for processing for the groove; (2) a laser beam for processing for the prepits shifted outward by a half-track pitch; and (3) a laser beam for processing for the prepits shifted inward by the same pitch. In addition, processing can be performed with two laser beams by setting a feed track pitch of a mastering apparatus in processing to be half of the track pitch in the physical format.
The above-described process using at least three laser beams to perform laser processing, as the background art, has problems in that the optical system of the mastering apparatus is large and complicated, and cancellation of laser beam interference is very difficult. The process performing laser processing, with a feed track pitch in a mastering apparatus set to be half of the track pitch in the physical format, has problems in that the processing time is doubled, and a processing signal generator is complicated.
Accordingly, the present invention is intended to solve the foregoing problems, and an object thereof is to provide a process that performs easy and efficient laser processing for a groove and prepits on one track on a master optical disk by a single processing scan, and a mastering apparatus provided with the function of the process.
A process for a master optical disk of the present invention has the following construction.
(1) A process for a master optical disk having a physical format in which in a land-and-groove-recording rewritable optical medium, a groove and a land are switched for each track, and prepits having no track-sector information on spirals identical to those of the groove are used to enable the reading of the track-sector information on the land and the groove by performing a single processing scan, wherein the prepits for the track-sector information, and an optical deflector using acoustooptic effects or an optical deflector using field-optical effects, are used to perform the optical deflection of a laser beam used for processing, and the use of a single processing scan performs laser processing for the groove and the prepits on one track.
(2) A process for a master optical disk having not only a physical format as set forth in (1) above but also a physical format in which a groove is wobbled at a frequency in a phase identical to that of an adjacent track, wherein the process comprises: storing a signal for the wobbling as digital data in a read-only memory; outputting the digital data in synchronization with an original clock signal for generating a process-for-prepits signal and a process-for-groove signal; applying to an optical deflector a composite signal of a wobbling signal generated by performing phase correction, and a signal for deflecting a laser beam inward and outward by a half-track pitch from the center of the groove; and using optical deflection based on the composite signal to perform laser processing for the groove and the prepits on one track by a single processing scan.
In addition, preferred embodiments in which the above-described process for a master optical disk is applied are shown below.
(a) A mastering apparatus provided with process (1) for a master optical disk.
(b) A mastering apparatus provided with process (2) for a master optical disk.
(c) A master optical disk processed by using mastering apparatus (a) or (b), and optical disks manufactured based on the master optical disk.